/**
 * UsageRollup — per-session/per-harness/per-tool token + cost tracker
 * driven by ProviderRuntimeEvents from the EventBus.
 *
 * The engine has no centralized usage rollup today. Each surface that
 * needs cost/latency information re-derives it from raw subprocess
 * output. With the event contract + bus in place, one subscriber can
 * compute everything once and serve it to every consumer (UI Billing
 * pane, /api/usage, telemetry, audit).
 *
 * Subscribes to two event types from the bus:
 *   - usage.updated         → input/output/reasoning tokens + cost
 *   - tool.call.completed   → per-tool latency timeline
 *
 * Plus state-machine events for session lifecycle bookkeeping:
 *   - session.created, session.shutdown
 *
 * Snapshots are exposed via:
 *   - sessionUsage(sessionId) → UsageSnapshot for one session
 *   - harnessTotals(harnessId) → aggregate across sessions
 *   - toolTimeline(sessionId, toolName) → ordered latencies
 *   - all() → full snapshot for export
 */
import type { EventBus, EventBusSubscription } from "./event-bus.js";
import type { HarnessId, SessionId, ToolCallId } from "./contracts/ids.js";
export interface UsageSnapshot {
    sessionId: SessionId;
    harnessId: HarnessId;
    inputTokens: number;
    outputTokens: number;
    reasoningTokens: number;
    estimatedCostUsd: number;
    toolCallCount: number;
    toolErrorCount: number;
    totalToolMs: number;
    startedAt?: string;
    endedAt?: string;
    lastUpdatedAt: string;
}
export interface ToolLatency {
    toolCallId: ToolCallId;
    tool: string;
    ok: boolean;
    elapsedMs: number;
    at: string;
}
export interface HarnessTotals {
    harnessId: HarnessId;
    sessionCount: number;
    inputTokens: number;
    outputTokens: number;
    reasoningTokens: number;
    estimatedCostUsd: number;
    toolCallCount: number;
    toolErrorCount: number;
}
export declare class UsageRollup {
    private readonly bus?;
    private readonly sessions;
    private readonly toolLatencies;
    private subscription;
    constructor(bus?: EventBus | undefined);
    /** Subscribe (or re-subscribe) to a bus. Returns the subscription handle. */
    subscribe(bus: EventBus): EventBusSubscription;
    /** Stop subscribing. The rollup keeps its accumulated data. */
    detach(): void;
    /** Drop all accumulated data. Useful for tests. */
    reset(): void;
    consume(event: import("./contracts/provider-runtime.js").ProviderRuntimeEvent): void;
    private toolNames;
    private findToolName;
    sessionUsage(sessionId: SessionId): UsageSnapshot | null;
    toolTimeline(sessionId: SessionId, toolName?: string): ToolLatency[];
    harnessTotals(harnessId: HarnessId): HarnessTotals;
    all(): UsageSnapshot[];
}